Keltner's latest co-authored work, "Social Class as Culture: The Convergence of Resources and Rank in the Social Realm," affirms this.

To test empathy, researchers studied video-taped interactions between strangers of different social classes, and found that overwhelmingly those of a higher social class were more disengaged -- "for instance checking their cell phone or doodling on a questionnaire, whereas lower-class individuals displayed more socially engaged eye contact, head nods, and laughs."

In another study, they looked at how high-school-educated participants were able to read facial expressions, and compared the results with those of college-educated participants. The less educated were much more spot-on with their "empathic accuracy."

Keltner says it comes down to this: "Unlike the rich, lower-class people have to depend on others for survival. So they learn 'prosocial behaviors.' They read people better, empathize more."